gpiolib: Refactor gpio_export

The gpio_export function uses nested if statements and the status
variable to handle the failure cases. This makes the function logic
difficult to follow. Refactor the code to abort immediately on failure
using goto. This makes the code slightly longer, but significantly
reduces the nesting and number of split lines and makes the code easier
to read.

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 46 insertions, 39 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5d6c71edc739..d5f9742d9ac1 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -702,8 +702,9 @@ int gpio_export(unsigned gpio, bool direction_may_change)
 {
         unsigned long           flags;
         struct gpio_desc        *desc;
-        int                     status = -EINVAL;
+        int                     status;
         const char              *ioname = NULL;
+        struct device           *dev;
 
         /* can't export until sysfs is available ... */
         if (!gpio_class.p) {
@@ -711,59 +712,65 @@ int gpio_export(unsigned gpio, bool direction_may_change)
                 return -ENOENT;
         }
 
-        if (!gpio_is_valid(gpio))
-                goto done;
+        if (!gpio_is_valid(gpio)) {
+                pr_debug("%s: gpio %d is not valid\n", __func__, gpio);
+                return -EINVAL;
+        }
 
         mutex_lock(&sysfs_lock);
 
         spin_lock_irqsave(&gpio_lock, flags);
         desc = &gpio_desc[gpio];
-        if (test_bit(FLAG_REQUESTED, &desc->flags)
-                        && !test_bit(FLAG_EXPORT, &desc->flags)) {
-                status = 0;
-                if (!desc->chip->direction_input
-                                || !desc->chip->direction_output)
-                        direction_may_change = false;
+        if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
+             test_bit(FLAG_EXPORT, &desc->flags)) {
+                spin_unlock_irqrestore(&gpio_lock, flags);
+                pr_debug("%s: gpio %d unavailable (requested=%d, exported=%d)\n",
+                                __func__, gpio,
+                                test_bit(FLAG_REQUESTED, &desc->flags),
+                                test_bit(FLAG_EXPORT, &desc->flags));
+                return -EPERM;
         }
+
+        if (!desc->chip->direction_input || !desc->chip->direction_output)
+                direction_may_change = false;
         spin_unlock_irqrestore(&gpio_lock, flags);
 
         if (desc->chip->names && desc->chip->names[gpio - desc->chip->base])
                 ioname = desc->chip->names[gpio - desc->chip->base];
 
-        if (status == 0) {
-                struct device   *dev;
-
-                dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
-                                desc, ioname ? ioname : "gpio%u", gpio);
-                if (!IS_ERR(dev)) {
-                        status = sysfs_create_group(&dev->kobj,
-                                                &gpio_attr_group);
-
-                        if (!status && direction_may_change)
-                                status = device_create_file(dev,
-                                                &dev_attr_direction);
-
-                        if (!status && gpio_to_irq(gpio) >= 0
-                                        && (direction_may_change
-                                                || !test_bit(FLAG_IS_OUT,
-                                                        &desc->flags)))
-                                status = device_create_file(dev,
-                                                &dev_attr_edge);
-
-                        if (status != 0)
-                                device_unregister(dev);
-                } else
-                        status = PTR_ERR(dev);
-                if (status == 0)
-                        set_bit(FLAG_EXPORT, &desc->flags);
+        dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
+                            desc, ioname ? ioname : "gpio%u", gpio);
+        if (IS_ERR(dev)) {
+                status = PTR_ERR(dev);
+                goto fail_unlock;
         }
 
-        mutex_unlock(&sysfs_lock);
-
-done:
+        status = sysfs_create_group(&dev->kobj, &gpio_attr_group);
         if (status)
-                pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
+                goto fail_unregister_device;
+
+        if (direction_may_change) {
+                status = device_create_file(dev, &dev_attr_direction);
+                if (status)
+                        goto fail_unregister_device;
+        }
 
+        if (gpio_to_irq(gpio) >= 0 && (direction_may_change ||
+                                       !test_bit(FLAG_IS_OUT, &desc->flags))) {
+                status = device_create_file(dev, &dev_attr_edge);
+                if (status)
+                        goto fail_unregister_device;
+        }
+
+        set_bit(FLAG_EXPORT, &desc->flags);
+        mutex_unlock(&sysfs_lock);
+        return 0;
+
+fail_unregister_device:
+        device_unregister(dev);
+fail_unlock:
+        mutex_unlock(&sysfs_lock);
+        pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
         return status;
 }
 EXPORT_SYMBOL_GPL(gpio_export);